The present embodiments relate to transistor circuits, and are more particularly directed to a memory with storage cells having silicon-on-insulator ("SOI") drive and access transistors with tied floating body connections.
The technology of many modern circuit applications continues to advance at a rapid pace, with one incredibly prolific type of circuit, and one which is highly developed, being digital memory. For such memories, consideration is given to all aspects of design, including maximizing efficiency and increasing performance. These considerations may be further evaluated based on the integrated circuit device in which the memory is formed, where such circuits may be implemented either as stand-alone products, or as part of a larger circuit such as a microprocessor. One often critical factor with respect to digital memories is the cost of the device and this cost is often affected by the overall size of the memory architecture. Another factor with respect to digital memories includes noise immunity. Thus, a desirable memory reduces device size and provides an acceptable immunity to noise signals.
In the current art, memory size may be affected by various factors. In one prior art approach as detailed later, memory size is affected by connections used for each of the drive and access transistors in each of the memory cells of the configuration. Specifically, it is known in the memory art for each memory cell to often include at least two access transistors, where access is through those transistors to corresponding storage nodes of the cell. It is further known to often include at least two drive transistors, where those transistors provide the ability to drive an output node through an access transistor, according to the state of the memory cell. In both cases, under current memory architectures these two types of transistors are sometimes formed using silicon-on-insulator (SOI) technology. In this instance, it is common to tie the body of each of the access and drive transistors to a fixed and relatively low potential. For example, often the bodies of the access transistors are tied to ground, while often the bodies of the drive transistors are tied to the source of the drive transistors, where the source itself is connected to ground. These connections are performed in the prior art so that the body of each transistor is fixed to a known potential, rather than permitting the body potential to fluctuate which could otherwise occur due to the tendency of the body potential to deviate due to the signal conditions experienced by the transistor. While these body-to-ground connections therefore provide acceptable operational performance, they also provide a drawback in that they require an additional connection per transistor and, thus, consume additional area on the integrated circuit in which the memory configuration is formed.
The above considerations and drawbacks are presented in more detailed fashion below. Based on that presentation, one skilled in the art will appreciate that there is a need to address these drawbacks. The preferred embodiments described below do indeed address these drawbacks, and thereby provide a more efficient and desirable integrated circuit configuration.